1. Field of the Invention
The present invention relates to a wet-type developing apparatus for use in a transfer-type electrophotographic machine such as an electrophotographic machine or a printer.
2. Discussion of Background
One method of producing recorded materials free from a smeared background at all times in a transfer-type electrophotographic machine such as an electrophotographic machine is to detect the potential of a latent image on the photosensitive body and apply an appropriate developing bias commensurate with the detected level to a developing electrode. The latent image potential can be detected through the developing solution in a wet-type developing apparatus. However, it is necessary to cover the detecting electrode completely with a latent image in order to detect the latent image potential accurately. Conventional wettype developing apparatus employ a developing electrode plate having an extremely large area. A potential induced via the developing solution from the photosensitive body is applied as a developing bias potential to the developing electrode plate. Since the latent image potential can accurately be detected only when a considerable portion of the latent image on the photosensitive body has entered a developing region, different developing bias potentials are produced before and after the latent image potential is detected, thus resulting in different image densities. This drawback can be solved by adding another detecting electrode having a smaller area for detecting the latent image potential, and applying a developing bias dependent on the detected potential level to the developing electrode plate. However, such a solution results in an increased cost.
Another problem is that tone is deposited on the detecting electrode and the developing electrode to form dielectric layers on the surfaces of the electrodes, preventing the electrodes from functioning properly. To eliminate this shortcoming, it has been customary to apply a bias to the electrodes in a direction opposite to the developing bias to clean the electrodes electrostatically except during the development of images. This process is nevertheless undesirable in that a large quantity of toner is deposited on the photosensitive body when the electrodes are electrostatically cleaned, thus placing a large burden on a device for cleaning the photosensitive body, and leading to toner deterioration.